Aspects of the Landuse and Landcover Change Dynamics of the Riparian Corridor of the New Calabar River, Nigeria

Abstract

Landsat 7 ETM Satellite imagery for 1987 and 2013 were used in a geographic information system to map and model changes in the Landuse and Landcover along the freshwater Riparian corridor of the New Calabar River. Percentage change in six Landuse-Landcover (LULC) features, namely Freshwater forest, Grassland, Barren-Sparse Vegetation, Scrub-Shrub, Agriculture and Urban/Builtup, were calculated from the differences between the pixels of the LULC in the imagery for 1987 and 2013. The pattern of changes along the buffer zones between 50 m and 500 m was a mixture of gains and losses in the LULC types. The freshwater forest declined between 0.6%-22%. In the Barren/Sparse vegetation category, there was a decline of between 9-16% but an increase of 323% was experienced at the 50 m buffer. The gains and losses were observed for the Grass category with 2-30% losses and 233% gain at the 50 meter buffer. Similar observations in the Scrub-Shrub category showed that losses were between 1.3-1.6% while a gain of 11% was observed at the 50 meter buffer. The Agriculture and Urban-Builtup maintained a significant increase across the buffer zones with values of 24-160% and 24-358% respectively. A grid based Riparian reach alteration zone modeling showed that high and extreme changes in LULC occurred mostly at the middle and lower reaches for Urban/Builtup (45%); Scrub-Shrub (34%); Barren/Sparse (40%). High and Extreme values in LULC extending to the Upper reaches were observed in Grass category (51%); Freshwater forest (40%) and Agriculture (55%). The cumulative composite model identified 33% of the grids with high and extreme value change coefficients in the middle and lower reaches. Grids of Moderate hotspots of change comprising 33% occurred at upper and lower reach zones of the Riparian study area. In all the chi-square statistics provide strong evidence of the differences (p =0.0382) that accounted for the composite variation within the Riparian reaches. It also provided evidence for the differences (p<0.0001) in the proportion of pixels that accounted for Gain and Loss of the different LULC types within riparian buffer zone in this study. The study provides information for targeting management objectives towards Riparian ecosystem resiliency for this section of the New Calabar River.